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#534 - sierramistfourteen (12/05/2012) [-]
wait, hold on... if you dug a hole to the middle of the earth... it only takes 45 min for a book to reach the bottom?    
Don't kill me... but why is that?
wait, hold on... if you dug a hole to the middle of the earth... it only takes 45 min for a book to reach the bottom?
Don't kill me... but why is that?
#620 to #534 - SubjectThree (12/05/2012) [-]
There are two things you have to consider when discussing gravity: terminal velocity  and the Coriolis Effect.   
   
Terminal velocity is the speed at which an object falls when it absolutely cannot fall any faster because the air resistance, or drag, pushing up on an object equals the force of gravity pushing down, resulting in zero-acceleration. Smaller objects, on average reach terminal velocity after dropping 1300 ft (to compare, the Empire State Building is about 1,450 feet tall. Assuming there is air inside the hole, the pressure of gravity on the air would counteract heat expansion. In other words, the book will soon approach its maximum falling speed before going half a mile down.   
   
Secondly, the Coriolis Effect, while most often associated with weather patterns, applies to anything affected by the Earth's rotation. Centrifugal force tells us that the lower parts of the tunnel are actually spinning faster than the upper parts because they are closer to the Earth's center of gravity. However, the book would be freefalling at a constant speed, as discussed, and would not speed up as it reaches the lower sections. That means that the book will no doubt slow, or even stop because the Coriolis Effect forces it to hit the sides of the tunnel, causing its fall speed to slow. IT may even cause the book to "stick" to the wall because the spinning Earth causes horizontal gravity that may even overpower vertical gravitry, but that is just my theory.   
   
So yes, 45 minutes does seem like a reasonable time to reach the bottom.
There are two things you have to consider when discussing gravity: terminal velocity and the Coriolis Effect.

Terminal velocity is the speed at which an object falls when it absolutely cannot fall any faster because the air resistance, or drag, pushing up on an object equals the force of gravity pushing down, resulting in zero-acceleration. Smaller objects, on average reach terminal velocity after dropping 1300 ft (to compare, the Empire State Building is about 1,450 feet tall. Assuming there is air inside the hole, the pressure of gravity on the air would counteract heat expansion. In other words, the book will soon approach its maximum falling speed before going half a mile down.

Secondly, the Coriolis Effect, while most often associated with weather patterns, applies to anything affected by the Earth's rotation. Centrifugal force tells us that the lower parts of the tunnel are actually spinning faster than the upper parts because they are closer to the Earth's center of gravity. However, the book would be freefalling at a constant speed, as discussed, and would not speed up as it reaches the lower sections. That means that the book will no doubt slow, or even stop because the Coriolis Effect forces it to hit the sides of the tunnel, causing its fall speed to slow. IT may even cause the book to "stick" to the wall because the spinning Earth causes horizontal gravity that may even overpower vertical gravitry, but that is just my theory.

So yes, 45 minutes does seem like a reasonable time to reach the bottom.
User avatar #565 to #534 - purpleacidboots (12/05/2012) [-]
Well it is a ******* long time o-O Imagine being in a free fall for 45 minutes, that's a lot.
User avatar #573 to #565 - AcidFlux (12/05/2012) [-]
The acceleration of gravity is 9.8m/s2. The radius of the Earth is 6.378 million meters.
User avatar #633 to #573 - purpleacidboots (12/05/2012) [-]
..I know xD and it's 9.82 m/s2 :b Sorry my physics teacher beat that into me xD
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